Ocean bottom seismic station

ABSTRACT

Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 11/313,275, filed Dec. 20, 2005, which claims benefit of U.S.provisional patent application Ser. No. 60/637,896, filed Dec. 21, 2004.Each of the aforementioned related patent applications is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to ocean bottom seismic(OBS) cables having arrays of sensor stations. More particularly,embodiments of the invention relate to multiple component sensorstations for cable termination and sensor integration within an OBScable array.

2. Description of the Related Art

Marine seismic exploration surveys for the exploration and monitoring ofhydrocarbon producing zones and reservoirs utilize seismic cables havingsensor arrays, i.e., a plurality of sensor stations interconnected bysections of cable. In general, the sensor stations include opticaland/or electrical sensors such as hydrophones, accelerometers and/orgeophones.

The cable arrays are typically deployed on the ocean floor from largedrums or spools. The spools require a large enough inner diameter toprevent damage to the sensor stations when the cable array is wrappedthereupon since the sensor stations may be larger and less flexible thanthe sections of cable connecting them. In order to maximize performance,the cable arrays may be buried in a predetermined pattern on the oceanfloor. Regardless of the particular method used to deploy the cablearray, deploying and optionally retrieving the cable array createssubstantial tension and stress on the cable array. For example,deploying the cable array off the back of a ship in deep water createssubstantial tension and stress on the cable array due to the weight ofthe cable array extending from the ship toward the ocean floor togetherwith the movement of the ship. Therefore, the cable array must includestrength elements designed to provide the primary axial load carryingcapability.

In general, the design of a cable array with integrated sensor stationsdetermines what flexibility is available in deploying, servicing andremoving the cable arrays. Deploying a cable having sensors is a complexoperation because the size of the sensor stations creates alongitudinally non-homogeneous cross section causing several limitationsin the handling of the cable. Further, the size and weight of the sensorstations and cable sets requirements on handling equipment andlimitations on possible length of each cable and on the number of sensorstations that can be integrated onto a cable length.

Cutting and splicing data transmission cables/fibers within the cablearray at each of the sensor stations increases time and cost whiledecreasing reliability. Design of the sensor station and/or cable arraycan affect how many splices are required at each station. Accordingly,any designs or techniques that reduce the number of splices of the datatransmission cables/fibers at each station decreases assembly time andcost while increasing reliability of the cable array.

Therefore, there exists a need for an inexpensive and improved cablearray and corresponding sensor station for use in ocean bottom seismic(OBS). There exists a further need for OBS cable arrays havingefficiently integrated sensor stations therein that are reliable,lightweight and low volume.

SUMMARY OF THE INVENTION

Embodiments of the invention generally relate to a sensor stationcapable of efficient cable termination and sensor integration within anocean bottom seismic (OBS) cable array. The sensor stations include ahousing for various sensor components. Additionally, the sensor stationscan accommodate an excess length of any data transmission members whichmay not be cut at the sensor station while enabling connection of one ormore cut data transmission members with the sensor components. Thesensor stations further manage any strength elements of the cable array.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a perspective view of a sensor station disposed along a cablewith a top cover of the sensor station shown transparent.

FIG. 2 is a perspective view of a base plate of the sensor station shownin FIG. 1.

FIG. 3 is a perspective view of an underside of the top cover of thesensor station shown in FIG. 1.

FIG. 4 is a perspective view of the sensor station with a biasing memberretracted to decouple the sensor station from the cable once tension isreduced.

FIG. 5 is a perspective view of the sensor station with cable noisereducing hoses surrounding the cable proximate the sensor station.

FIG. 6 is a perspective partial cut away view of a sensor stationdisposed along a cable.

FIG. 7 is a perspective view of a base plate of the sensor station shownin FIG. 6.

FIG. 8 is a perspective view of the cable coupled to a strength memberof the sensor station shown in FIG. 6.

FIG. 9 is a perspective partial cut away view of a sensor stationdisposed along a cable without severing strength elements of the cable.

FIG. 10 is a perspective view of a sensor station disposed along acable.

FIG. 11 is a cross section view of the sensor station shown in FIG. 10.

FIG. 12 is a perspective view of a sensor station disposed along a cablewith bend limiters disposed around the cable on each side of the sensorstation.

FIG. 13 is an exploded view of a base plate of the sensor station shownin FIG. 12 holding the cable.

FIG. 14 is an exploded view of a connector within the sensor stationshown in FIG. 12 for coupling to strength elements of the cable.

FIG. 15 is a perspective view of a sensor station during a fabricationprocedure that provides an excess length of only one element within amulti-element cable at each station to enable splicing with the oneelement.

DETAILED DESCRIPTION

Embodiments of the invention generally relate to a sensor stationdisposed in an ocean bottom seismic (OBS) cable array. Obtaining an OBSsurvey requires placing the cable array along the ocean floor,generating seismic waves that travel downward through the earth andreflect off underground deposits or changes in formation, and recordingthe reflected seismic waves detected by the sensor stations. When thecomponents of the sensor station are all optical as described herein forsome embodiments, the cable includes an optical waveguide fortransmission of optical signals to and from the optical components.However, the sensor station may alternatively include any combination ofhydrophones, accelerometers and/or geophones, which may be electricalcomponents connected to an electrically conductive cable fortransmission of data from the electrical components and/or opticalcomponents.

Since strength elements in the cable arrays make the cable array stiff,the high rigidity of the cable array allows noise transmitted into onepart of the cable array to migrate throughout the cable array to thesensor stations along the cable array. According to some aspects of theinvention, the sensor stations can remain seismically decoupled from thesections of cable during seismic surveying in order to reduce noise.However, the entire cable array must have sufficient strength duringdeployment to accommodate the tension and stress thereon until thetension reduces when the cable array is positioned on the ocean floor.Even if the cable is seismically decoupled from the sensor stationitself, the cable proximate the sensor station can make the groundaround the station move such that it may also be required to seismicallydecouple the cable proximate the sensor station in order to furtherreduce noise transmitted across the cable.

FIG. 1 shows a sensor station 100 disposed along a cable 102. Inpractice, the entire length of the cable 102 includes an array formed bya plurality of the sensors stations 100 spaced apart along the cable102. The sensor station 100 includes a housing or top cover 104 (showntransparent) disposed on top of a base plate 106 that supports, in oneembodiment, one optical hydrophone 11 and three orthogonally orientedoptical accelerometers 12, 13, 14 beneath the top cover 104. The cable102 can include an optical waveguide member 108, at least one strengthelement that is shown as two strength elements 110 on each side of theoptical waveguide member 108 and an outer covering 112 surrounding theoptical waveguide member 108 and the strength elements 110.

FIG. 2 illustrates the base plate 106 of the sensor station 100. Thebase plate 106 may be made by cost effective molding and includes acenter portion 200 and flexible tapered end portions 202 on oppositesides of the center portion 200. As in one alternative embodiment shownin FIG. 1, the strength elements 110 of the cable 102 may terminate ateach end of the sensor station 100 and mechanically couple to the baseplate 106. Specifically, the terminated strength elements 110mechanically couple to the flexible tapered end portions 202 of the baseplate 106. The terminated strength elements 110 may couple to the baseplate 106 by appropriate fixing (e.g., welding or clamping) of the endsof the terminated strength elements 110 after the ends have beeninserted into end apertures 204 extending through the end of the taperedend portions 202. Thus, the base plate 106 must withstand the requiredstrain during deployment since the strength elements 110 of the cable102 mechanically couple at each end of the base plate 106.

Voids 206 through the tapered end portions 202 increase flexibility ofthe base plate 106 at the tapered end portions 202. For someembodiments, the top cover 104 may not fix to the tapered end portions202 in order to not affect the flexibility of the tapered end portions202. This flexibility of the tapered end portions 202 where the strengthelements 110 of the cable 102 couple to the sensor station 100 aids inboth the ability of the sensor station 100 to be wound onto a spool andthe seismic decoupling of the sensor station 100 from the cable 102since the strength elements 110 are the most stiff portion of the cable102.

Central flexible guides 208 extend from the center portion 200 of thebase plate 106 to the ends of the base plate 106 where the cable 102couples thereto. The guides 208 provide a protected passage 210 to andfrom the center portion 200 for the optical waveguide member 108 of thecable 102. The center portion 200 provides a generally stiffer area thanthe tapered end members 202 and provides an area within a profile 212where the hydrophone 11 and accelerometers 12, 13, 14 are located afterbeing coupled to the optical waveguide member 108 of the cable 102.Typically, coupling the optical waveguide member 108 to the hydrophone11 and accelerometers 12, 13, 14 includes terminating and splicingoptical fibers of the optical waveguide member 108 to the hydrophone 11and accelerometers 12, 13, 14. An additional element 15 may be includedfor packaging of any possible required fiber optic components such ascouplers used to connect the hydrophone 11 and accelerometers 12, 13, 14to each other and/or the waveguide member 108.

FIG. 3 shows the underside of the top cover 104 of the sensor station100. The top cover 104 may be made by cost effective molding andincludes a center sensor cavity 300 and ribs 302 between the sensorcavity 300 and the outer walls of the top cover 104. Preferably, the topcover 104 and/or the base plate are molded from composites. The ribs 302of the top cover 104 make the top cover 104 very rugged to preventdamage to the hydrophone 11 and accelerometers 12, 13, 14 duringdeployment and permit the sensor station 100 to withstand burying.

The shape of the top cover 104 corresponds to the shape of the baseplate 106. Further, the sensor cavity 300 of the top cover 104 mateswith the profile 212 in order to seal the sensor cavity 300 once thehydrophone 11 and accelerometers 12, 13, 14 are in place and coupled tothe optical waveguide member 108. Once sealed, the sensor cavity 300 maybe filled with a protective oil to make a pressure balanced cavity thateliminates the need for high rated pressure barriers. The oil alsoensures a good acoustic coupling for the hydrophone 11 with the underwater pressure changes.

FIG. 4 illustrates the sensor station 100 with a biasing member 400retracted to further decouple the sensor station 100 from the cable 102once tension is reduced (e.g., after deployment). In the embodimentshown, the strength elements 110 connect with the biasing member 400 viaa connector 402 that has a larger diameter than the end apertures 204 ofthe base plate 106. Thus, interference between the end apertures 204 andthe connector 402 provides an end stop with high strength to take theload during deployment as shown in FIG. 1. However, the tension reduceswhen the sensor station 100 is positioned on the sea floor such that thebiasing member 400 attached to an opposite end of the tapered endportions 202 pulls the connector 402 away from the end apertures 204 asillustrated in FIG. 4, thereby reducing the seismic coupling between thecable 102 and the sensor station 100. The biasing member 400 may be aspring, an elastomer or any other type of elastic element. In general,any coupling assembly that couples the strength elements 110 of thecable 102 to the sensor station 100 that utilizes a biasing member withan end stop to selectively transfer tension during deployment may beused to further decouple the sensor station 100 from the cable 102.

FIG. 5 shows the sensor station with two cable noise reducing hoses 500surrounding the cable 102 proximate the sensor station 100. Each of thehoses 500 mount to opposite ends of the base plate 106 and may extendbetween approximately 0.5 and approximately 2.0 meters from the sensorstation 100. The hoses 500 aid in seismically decoupling the cable 102from the ground close to the sensor station 100 once the sensor stationis deployed. In this regard, the hoses 500 around the cable 102 reducefriction between the cable 102 and the ground along the length of thehoses 500. The cable 102 fits loosely within the hoses 500 without beingdirectly secured to the hoses 500 in order to permit movement therein.An inside of the hoses 500 provide a friction coefficient sufficientlylow to not inhibit movement of the cable 102 within the hoses 500.Accordingly, the inside surface of the hoses 500 may be coated with aTeflon layer. The hoses 500 may be a corrugated plastic with a metalspiral spring inside to enable flexibility while withstanding radialcompression when buried into the ground.

FIG. 6 illustrates a partial cut away view of a seismic sensor station600 disposed along a seismic composite cable 602. The station 600includes a base plate 604 for cable termination and protection of anexcess length of a first optical cable 606 of the composite cable 602,as shown in FIG. 7. The first optical cable 606 bypasses the station 600and is not cut in two at the station 600 such that the excess length iscoiled into a recessed central portion of the base plate 604. A secondoptical cable of the composite cable 602 is cut to provide first andsecond termini 607, 608 that enable splicing with optical components 610of the sensor station 600. The optical components 610 mount onto thebase plate 604 above the recessed portion holding the first opticalcable 606. A housing 605 mounts onto the base plate 604 to enclose theoptical components 610.

The first optical cable 606 may not be cut at the station 600 to reducelosses of signals from the stations along the cable 602, to decreasecost and to improve reliability. For example, one or multiple fiberswithin the first optical cable 606 (e.g., fiber(s) in metal tube) mayproceed to other stations along the cable 602. At any of these otherstations, one or more of these fibers that were not cut in the firstoptical cable 606 can be cut to provide termini for splicing to opticalcomponents. Accordingly, the stations can be multiplexed with a desirednumber of the stations per optical fiber without unnecessary cutting andsplicing of the fibers/cables.

The base plate 604 can include a strength member 612 shown in FIG. 8 totransfer load between first and second regions 601, 603 of the cable602. For example, cut ends of strength elements (not shown) within thecomposite cable 602 can couple to the strength member 612 in a mannersimilar to other couplings of cable strength elements described herein.The strength member 612 can be formed of metal and disposed within alongitudinal recess of the base plate 604.

FIG. 9 illustrates a seismic sensor station 900 disposed along acomposite cable 902 having strength elements 907 as well as first andsecond optical cables 906, 908. The first optical cable 906 can includemultiple fibers within a metal tube and bypasses the sensor station 900without being terminated. For example, the first optical cable 906 canbe arranged on an outside surface of an internal sensor housing 910 soas to continue in a continuous manner to the next station along thecomposite cable 902. The second optical cable 908 can include a singleoptical fiber within a metal tube and can be terminated inside thesensor station 900 to connect thereto.

An external shroud 912 defines a space between the outside surface ofthe internal sensor housing 910 and an inside surface of the externalshroud 912 for allowing a length of the first optical cable 906 to beloosely arranged at least partly within the space while alsomechanically protecting the second optical cable 908 from the externalenvironment. The outside surface of the internal sensor housing 910 canrepresent a generally circular or elliptical shape for coiling the firstoptical cable 906 around.

Additionally, the strength elements 907 of the composite cable 902 canbe coiled up without cutting similar to the first optical cable 906. Thestrength elements 907 can lock onto the internal sensor housing 910 bytensioning the cable 902. The internal sensor housing 910 takes loadthrough a squeezing effect when the cable 902 is pulled at full load.Guide members 914 guide the strength elements 907 at ends of the sensorstation 900 to control a path of the strength elements and forces duringbending at tension.

FIG. 10 illustrates a seismic sensor station 1000 that has a circularand symmetric design and is disposed along a composite cable 1002. Acylindrical shaped internal housing 1010 provides an outside surfacewhere a first optical cable 1006 of the composite cable 1003 is coiled.Since the first optical cable 1006 is not cut, the first optical cable1006 defines a loop that wraps onto the internal housing 1010 from bothends of the internal housing 1010 towards a central region of theinternal housing 1010 where a midpoint of the loop is disposed. Cablecoupling members 1024 are fastened to each end of the housing 1010.

FIG. 11 shows a section view of the sensor station 1000. The sensorstation 1000 includes sensor components 1011 disposed inside the housing1010 and an external shroud 1012 (not shown in FIG. 10) surrounding aregion of the housing 1010 where the first optical cable 1006 has beenrouted to and coiled around. First and second passages 1014, 1016through the housing 1010 enable routing of a second optical cable intoand out of the housing 1010 for connection to the sensor components1011.

Each of the cable coupling members 1024 includes a split body 1018fastened together to define an internal conical bore for matingengagement with a conical member 1020. The conical member 1020 istightened down around a strength section of the cable 1002 via bolts1022 threaded into the body 1018. The first and second optical cables1006, 1008 extend through the conical wedge 1020 from within aconcentric central region of the cable 1002 that is gripped by theconical wedge 1020. For some embodiments, the first optical cable 1006can be disposed within the concentric central region while the secondoptical cable 1008 can replace one or more armor wires/cables of thestrength section of the cable 1002.

FIG. 12 illustrates a seismic sensor station 1200 disposed between firstand second bend limiters 1201, 1202 disposed along a composite cable1210. The bend limiters 1201, 1202 along with the cable 1210 provideflexibility extending from the station 1200. Additionally, each of thebend limiters 1201, 1202 can be made of rubber and can prevent kinks ofthe cable 1210 that loosely passes through a channel through the bendlimiter.

The sensor station 1200 includes a base member 1204 that a top cover1205 is secured to. The bend limiters 1201, 1202 can fix to the topcover 1205 and/or base member 1204 by bolts or other fasteners. Similarto other embodiments described heretofore, an interior volume defined bythe base member 1204 and top cover 1205 houses sensor components (notshown). The base member 1204 is structurally rigid and can be made ofmetal such as steel to accept loads across the cable 1210 at the station1200.

FIG. 13 shows an exploded view of a bottom side of the base plate 1204adapted for holding the cable 1210. The base plate includes a recessedregion 1212 for holding a coil of excess length of a first optical cable1206 of the composite cable 1210. Additionally, the base plate 1204defines a cavity 1214 configured to secure each connector member 1220coupled to the cable 1210. First and second clips 1216, 1218 fasten intothe base member 1204 over the cable 1210 to aid in holding the cable1210 properly within the base member 1204.

FIG. 14 illustrates an exploded view of the connector member 1220 forcoupling to first and second strength elements 1222, 1224 of thecomposite cable 1210. Stripped portions of the strength elements 1222,1224 pass through respective conical bores in the connector member 1220.First and second conical inserts 1226, 1228 are disposed centrallybetween strands of, respectively, the first and second strength elements1222, 1224. Each of the conical inserts 1226, 1228 has a corrugatedconical surface that engages the corresponding strength elements 1222,1224 for self locking of the strength elements 1222, 1224 within theconnector member 1220 when tension is applied to the cable 1210.Squeezing of the strength elements 1222, 1224 between the connectormember 1220 and the conical inserts 1226, 1228 that cannot pass throughthe bores in the connector member 1220 affixes the connector member 1220with respect to the strength elements 1222, 1224.

With reference to FIGS. 12-14, assembly of the sensor station 1200includes stripping an area of the composite cable 1210, cutting thestrength elements 1222, 1224, preparing the connector members 1220, andcutting a second optical cable 1208 in a central region of the area ofthe composite cable 1210 that is stripped. The optical cables 1206, 1208can each be fiber(s) in a metal tube (FIMT). Assembly progresses bypositioning ends of the second optical cable 1208 through apertures inthe base member 1204 and bonding and sealing of the second optical cable1208 within the apertures. Locking down the clips 1216, 1218 holds thecable 1210 to the base member 1204 with the connector members 1220 inthe cavity 1214 to prevent movement relative to the base member 1204.Coiling of the first optical cable 1206 for placement into the recessedregion 1212 occurs without cutting the first optical cable 1206 orotherwise altering the (FIMT) such that the first optical cable 1206resists undesirable bending. Placing a bottom cover 1203 over therecessed region 1212 protects the optical cables 1206, 1208 and furthermaintains the connector members 1220 within the cavity 1214.

Splicing the second optical cable 1208 with the optical componentsdisposed on top of the base member 1204 can occur since the secondoptical cable 1208 is cut with ends extending through the base member1204. Securing the top cover 1204 to the base member 1205 encloses theoptical components. Fixing the bend limiters 1201, 1202 to the top cover1205 and base member 1204 completes the assembly of the sensor station1200. For some embodiments, the bend limiters 1201, 1202 are not splitsuch that it may be necessary to feed the appropriate bend limiters1201, 1202 onto the cable 1210 prior to assembling the station 1200.

A first interior volume between the top cover 1205 and the base member1204 can be sealed while a second interior volume between the bottomcover 1203 and the base member 1204 may not be sealed. For someembodiments, the top cover 1205 may be ported to communicate pressure toat least an area of the first interior volume where a hydrophone of theoptical components is located. Portions of the optical cables 1206, 1208within the second interior volume can be maintained as the FIMT sincethe first optical cable 1206 is uncut and the second optical cable 1208can enter the first interior volume as the FIMT.

FIG. 15 shows a sensor station 1500 during a fabrication procedure thatprovides an excess length of a second optical cable 1508 within amulti-element cable 1510 at each station to enable splicing of thesecond optical cable 1508 with sensor components (not shown). For someembodiments, the multi-element cable includes strength elements 1522,1524, a hollow passage tube 1509 and a first optical cable 1506 such asa multi-fiber FIMT. As previously discussed, the first optical cable1506 can contain a plurality of waveguides or fibers that pass throughthe sensor stations. At desired locations, one or more waveguides orfibers within the second optical cable 1508 can crossover with orpick-up one or more of the waveguides in the first optical cable 1506 toenable splicing into different transmission paths.

Similar to the sensor station 1200 shown in FIG. 12, the sensor station1500 can be disposed between bend limiters 1502 (only one is shown).Additionally, the sensor station 1500 includes an interior volumedefined by a base member 1504 and a top cover 1505 that houses thesensor components. Assembly of the sensor station 1500 includesstripping an area of the multi-element cable 1510 to expose at least thepassage tube 1509 and cutting the passage tube 1509 without cutting thestrength elements 1522, 1524 or the first optical cable 1506. Thestrength elements 1522, 1524 and the first optical cable 1506 passstraight through the station 1500. Assembly progresses by pulling thesecond optical cable 1508 through the passage tube 1509. For someembodiments, the passage tube 1509 can include a metal wire used to pullthe second optical cable 1508 off a drum 1525 and through the passagetube 1509. This procedure of feeding the second optical cable 1508through the passage tube 1509 progresses between each station in orderto continue to subsequent stations along the multi-element cable 1510. Adesired length of the second optical cable 1508 can be pulled out orremain left out of the passage tube 1509 to accomplish station splicing.The second optical cable 1508 can be coated with a polymer material toprevent corrosion inside the passage tube 1509.

One end of the second optical cable 1508 pulled from the passage tube1509 at the station 1500 is disposed through an entrance aperture 1511in the base member 1504 and can be bonded and sealed within the entranceaperture 1511. As the fabrication procedure progresses to the subsequentstations, another end of the second optical cable 1508 remaining out atthe station 1500 is disposed through an exit aperture 1513 in the basemember 1504 and can be bonded and sealed within the exit aperture 1513.Splicing the second optical cable 1508 with the optical componentsdisposed on top of the base member 1504 can occur since the secondoptical cable 1508 has these ends with sufficient excess lengthextending through the base member 1504.

The station 1500 clamps to the multi-element cable 1510. Securing abottom cover 1503 to the base member 1504 can fix the station 1500 at aposition along the multi-element cable 1510 by sandwiching themulti-element cable 1510 between the bottom cover 1503 and the basemember 1504. For some embodiments, gripping teeth 1507 disposed on eachend of the bottom cover 1503 facilitate clamping of the multi-elementcable 1510.

A method of integrating a sensor station in an ocean bottom seismiccable array includes providing a cable of the ocean bottom seismic cablearray having one or more strength elements and a data transmissionmember and coupling a base plate of a sensor station to a terminated endof the strength elements, wherein the base plate is substantiallyseismically decoupled from the cable at tensions between the base plateand cable below a predetermined value.

Features and aspects of any of the embodiments described herein can becombined or otherwise modified with any features or aspects of otherembodiments described herein. While the foregoing is directed toembodiments of the present invention, other and further embodiments ofthe invention may be devised without departing from the basic scopethereof, and the scope thereof is determined by the claims that follow.

1. A seismic sensor station for disposal on a seismic cable, comprising:an internal housing supporting sensor components of the sensor station,wherein an outside wall of the housing defines a rounded perimeter ofthe internal housing; a first optical cable of the seismic cable that isuncut at the sensor station and coiled around a circumference of therounded perimeter of the internal housing; a second optical cable routedinto the housing for connection to the sensor components; and anexternal shroud disposed over the internal housing and first opticalcable.
 2. The seismic sensor station of claim 1, further comprising aguide member to couple to a strength element of the seismic cable atends of the sensor station.
 3. The seismic sensor station of claim 1,wherein the first optical cable defines a loop that wraps onto theinternal housing from both ends of the internal housing towards acentral region of the internal housing where a midpoint of the loop isdisposed.
 4. The seismic sensor station of claim 1, wherein the internalhousing has first and second passages through the housing to enablerouting of the second optical cable into and out of the housing.
 5. Theseismic sensor station of claim 1, wherein cable coupling members arefastened to each end of the internal housing.
 6. The seismic sensorstation of claim 5, wherein each of the cable coupling members includesa split body fastened together to define an internal conical bore formating engagement with a conical member tightened down around a strengthsection of the seismic cable.
 7. The seismic sensor station of claim 6,wherein bolts are threaded into the split body to tighten the conicalmember around the strength section.
 8. The seismic sensor station ofclaim 1, wherein the rounded perimeter of the internal housing isdisposed between first and second end faces of the internal housing todefine a cylindrical shape of the internal housing.
 9. The seismicsensor station of claim 8, wherein the first and second end facesrespectively have first and second passages through the housing toenable routing of the second optical cable into and out of the housing.10. The seismic sensor station of claim 8, further comprising first andsecond cable coupling members fastened respectively to the first andsecond end faces of the internal housing.
 11. The seismic sensor stationof claim 8, further comprising first and second conical shaped cablecoupling members fastened respectively to the first and second end facesof the internal housing.
 12. The seismic sensor station of claim 8,wherein the outside wall of the housing defines the rounded perimeterwith a first section between two relatively larger diameter secondsections that the first optical cable is disposed between.